Fluid pressure producing device



Feb. l0, 1942. H, C BQWEN I '2,272,316

FLUID PRESSURE PRODUCING DEVICE Filed' May 20, 1957 2 Sheets-Sheet 1 20 INVENTOR. F 2 E 22 Hcesfercaww BY 7% @QM f Feb. 1o, 1942. H. C. BQWEN 2,272,316

FLUID PRESSURE PRODUCING DIEVICE.

Filed May 20, 1957 2 Shee'ts-Sheet 2 //a ,0 l V a 30.

v INVENTOR #teaser C Bamsw- BY MM Patented Feb. 10, 1942 FLUID PRESSURE PRoDUolNG DEVICE Herbert C. Bowen, Detroit, Mich., assignor to Hydraulic Brake Company, Detroit, Mich., a corporation of California Application May 20, 1937, Serial No. 143,693

4 Claims. (Cl. 60- 54.6) This invention relates to fluid pressure braking systems and more particularly to uid pressure producing devices for such systems.

An object of the invention is to provide a fluid pressure producing device operative to electively increase the pressure on the fluid without proportionately increasing the applied operating force.

Another object of the invention is to provide a uid pressure producing device operative to effect a transition from: low to high pressure without pulsations in the uid during the operation thereof.

Other objects of the invention will appear from the following description taken in connection with the drawings forming a part of this specication, and in which- Fig. 1 is a diagrammatical illustration of a fluid braking system embodying theinvention;

Fig. 2 is a vertical sectional view of the uid pressure producing device illustrating the piston Nthereof in retarded position;

Fig. 3 is a vertical sectional view of the iluid pressure producing device partly broken away illustrating the piston in advanced position;

Fig. 4 is a sectional view substantially on line y 6 4, Fig. 3; and

Fig. 5 is a sectional view substantially on line 5 5, Fig. 3.

Referring tothe drawings for more specific details of the invention, Ill represents a iluid reservoir having a removable top I2 provided with a lling opening I4 which may be closed as by a cap I6 having openings I8 for venting the reservoir to the atmosphere. The reservoir also has a drain opening 26 which may-be closed as by a plug 22, and arranged on the wall of the reservoir adjacent the bottom thereof is an opening 24.

A cylinder 26 iitted in the opening 24 has a radial ange 28 bearing lagainst a wall of the reservoir and secured thereto as by bolts 30 so as to support the cylinder within the reservoir adjacent the bottom thereof. The cylinder includes a large chamber 32 having one end opening into the reservoir and its other end communicating with a relatively small chamber 34 arranged concentrically to the large chamber and providing at its junction with the large chamber an annular shoulder 36. The large chamber has a port 38 providing a communication between the chamber and the reservoir, and the small chamber has a head 40 provided with a discharge port 42.

A fluid pressure delivery pipe er conduit 44 suitably connected to the discharge port 42 has branches connected respectively to iluid pressure actuated motors 46 arranged in pairs, one pair for actuating the brakes associated with the front wheels of a vehicle and another pair for actuating the brakes associated with the rear wheels of the vehicle.

As shown, the brakes are'of conventional type each including a xed support or backing plate 68, a rotatable drum 50 l associated Atherewith which may be secured to a wheel, a pair of corresponding interchangeable lfriction elements or shoes 52 pivoted onthe backing plate, and a motor corresponding to the motors 46 mounted on the backing plate between the shoes and operative to spread the shoes into engagement with A the drumv 50 against the resistance of a retractile spring 54 connecting the shoes so as to ef.- iectively retard rotation of the drum.

A compound piston reciprocable in the cylinder is held against displacement by a retaining ring 56 seated in a groove in the wall of the cylinder adjacent the open end of the large chamber 32.- This retaining ring also serves as a seat for the compound piston when in its fully sion 62 projecting into the small chamber 34, and

the extension is diametrically and axially bored as indicated at 64 to provide a communication between that portionof the chamber 32 forward ,of the piston 58 and the interior of the piston.

A plurality of passages 66 in the wall of the shell provide communications between the reservoir an`d that portion of the cylinder forward of the piston. A sealing cup 68 seated on the head 62 controls the passages 66, and a spring 'l0 interposed between the cup and an annular washer ll seated on the shoulder 36 at the junction of the large and small chambers retains the cup against displacement. The spring l0 also assists in the return of the piston to its retracted position.

A combinedthrust block and valve 12 reciprocable inl the piston 58 includes a body portion 14 havingl passages or ports 16 therein and corresponding concentric oppositely disposed end portions 18 and 88. The portion 88 is provided at its free end with a diametral groove 82 adapted to register with the passage 64 in instances the piston 50 and that pfrtion of the chamber 32 forward of the 'piston 58. A retaining' ring 34 suitably secured' in the open end of thepiston 50 has thereon an annular rubber washer 30 providing a suitable seat for the valve, and a heavy spring sleeved on the-end portion 30 between the body portion 'I4 and the backv piston 94 reciprocable in the small chamber 34.

'I'his piston is characterized by a shell, closed at one end as by a head 96 and open at its other end. The open end -has an internalslot 00 providing an annular shoulder |00.V The s lot` receives the collar 90 and is of suiiicient width to provide for `relative movement between the piston'and the collar, the movement being limited by the annular shoulder |00. A retaining ring |02 seated in a groove in the wall of the shell adjacent the open end'ther'eof retains the piston against displacement, and a very. light spring |04 interposed between the,collar and back of the head 00 normally retains the piston in advanced position.

The head 96 ofthe small piston normally seated .on the washer 1| has a plurality of spaced ports |06 and an axial port |00, the latter being adapted to receive the free end of the extension 02 during the compression stroke of the piston. 'Ihe spaced ports.|00 and the axial port |00 provide communications between the large cham- Upon further advance of the piston the pressure on the iluid in the large chamber 32 and A the small chamber 34 increases the load on the ber 32 and themsmall chamber 34. A collapsible sealing cup ||0 having a concentric opening-y -registering with the port |00 in the head 00 is seated on the head and is retained against displacement by a return spring` I4 interposedbetween the cup and a two-way valve ||0 seatedu on theI head of the cylinder for control of the discharge port 42. 'Ihe cup |I0 controls the spaced ports |00 and also cooperates with the extension 02 to seal the axial port |00 during the compressionstroke of the piston.

A transverse shaft H0 suitably mounted inthe wall of the reservoir has keyed thereto within the reservoir an actuator |20 engaging the force applying end of the thrustv block 12, and an arm |22 suitably secured tothe shaft outside of the reservoir is connected as by a rod |24 to a foot pedal lever |20 pivoted 4as indicated at |28 and connected by a retractile spring |30 to a xed support |32. A

In a normal operation of the system upon depressing 4the footpedal lever |20 force is transmitted `from the lever through the rod |24, the arm |22, the shaft ||0 and the actuator |20 to the piston, resulting in moving the piston on its compression stroke. During the initial movement of the piston on its compression stroke, the cup 00 on the head 00v of the large piston closes thevport 30, and the extensionA 02 on the head 00 of the large piston is advanced to close the axial port |00 in'the head 00 of the small piston.

As the piston advances on its @compression stroke the fluid in the chanmber 32 forward of valve 12. This increase ofthe load on the valve materially -assists the heavy spring 00 in retainingV the valve 12 in closed position. When the .pressure on the iluid 1n the chambers reaches a predetermined pressure oll'ering substantial resistance to movement of the piston and the valve '|2, the applied operating force on the valve overcomes the load on the valve imposed by the pressure on the uid and the heavy spring 00, resulting in' movement of the valve from its seat- Upon opening of this` valve, the pressure on the iluid in the chamber 32 is released and a small quantity of iiuid is returned from the chamber 32 through the passage 04 in the large piston and the ports 'i6 to the reservoir.

Simultaneously with this operation the pressure on the iluid in the system is received on the head 96 of the small piston where it does not .oii'er sufficient resistance to movement of the piston to retain the spring 00 compressed. This results in a slight advance of the piston under the influence of the spring 03 accompanied by closing of the valve 12, and as the piston provceeds on' its compression stroke pressure isagain the valve 12 again opens and establishes communication between the chamber 32 and the reservoir. At this stage the valve opens very slowly so that the iluid is metered from the chamber 32 past the valve and into the reservoir at a rate affording a constantly decreasing resistance to the movement of the large piston and thus accomplishing the transition from low to high pressure without pulsations in the pressure pro ducing means.

As a result of the foregoing transition, the

' parts assume the position shown in Figure 3 oi the large piston is displaced therefrom through 4 the small piston past the, cup |I0 through the 75 00 and the piston moves the drawings wherein the large piston is entirely inoperative and the small piston receives the full force exerted on the foot pedal and translates it into pressure on the uid in the small cylinder 34, the conduits and the wheel cylinders. Because of the small area of this piston 94 and the leverage and linkage, the operator can create any desired degree of braking action without undue effort by merely continuing to exert force on the oot pedal.

At the conclusion of a braking operation, the

foot pedal 'lever |20 is' released and returns to its retracted postion under the iniiuence of the retractile spring |30, and simultaneously therewith the actuator |20 connected to the foot peda lever by suitable e moves to its retractec position. 'I'hls resul in release of the valve Il and consequently of the piston, whereupon the valve 'I2 closes under the iniiuence of the spring to its retracted posiprovided by the foot pedal.

tion under the inuence of the retractile springs and, H4. vDuring this movement the small piston is slightly, advanced under the inuence of the spring |04 as it moves to its seat on the annular washer 1l, resulting in opening the port |08 and retaining this port open when thev piston is in retracted position.

During this operation fluid is'returning from l the motors 46 and the iiuid pressure delivery pipe or conduit 44 and its branches to the cylinder, and any excess of uid over and above the quantity necessary to completely illv the cylinder is returned to the reservoir by way ofthe Port 38.

The subject-matter disclosed herein is claimed more broadly in my copending application, Serial No. 689,715, led September. 16 1933, and issued as Patent No. 2,196,190,0n April 9, 1940.

Although this invention has been described in connection with' certain specic embodiments, the principles involved are susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is, therefore, to be limited only by the scope of the appended claims. v

Having thus described the various features of Ythe invention, what I claim as new and desire to secure by Letters Patent is 1. A iiuid pressure producing device of the class described, comprising a cylinder having a double diametral bore providing a large chamber and a relatively small chamber, a reservoir for supplying fluid to saidA chambers, a discharge port in the small chamber, a piston reciprocable in each chamber, means connecting said pistons,

by-pass means permitting now of uid past the f smaller piston in one direction only during advancement of said pistons, av chamber in the larger piston, circumferential passages in th'e larger piston connecting the piston chamber with the reservoir, a passage connecting the larger chamber and piston chamber, a valve normally closing said passage, said passage being opened by movement of said valve in the direction of advancement of said pistons to create pressure y in said llarger and smaller chambers, a spring interposed between said valve and said larger piston and normally holding said valve closed, said spring together with fluid pressure on the 'area i of the valve being acted upon by the reactions double diametral bore providing a large chamber and a relatively small' chamber, a reservoir for supplying uid to said chambers, a discharge port in the small chamber, a hollow piston reciprocable in each chamber, means connecting said pistons, a port connecting the reservoir with the'larger chamber, a cup washer movable with the larger piston to control said port, bypass 'means in the smaller piston permitting ow of fluid past the smaller piston in one direction only during advancement of said pistons, a passage through the larger piston connecting the larger chamber with the reservoir, a valve normally closing said passage, said valve being opened by movement of said valve in the direction of advancement of said pistons to create pressure in said chambers, vva spring interposed between said valve and said pistons and normally holding said valve closed, said spring being acted upon by the reactions exerted on said pistons by the fluid pressures in said chambers less that degree of reaction exerted in the large chamber acting on the inner side of the valve, and yielding under a predeterminedreaction to permit relative movement between the pistons and said valve to open the valve and relieve the-fluid pressure in the larger chamber and means for applying force to said valve to advance said pistons.

3.1A iiuid pressure producing device of the class described, comprising a cylinder h'aving a double diametral bore providing a large chamber and a, relatively small chamber, a reservoir for supplying fluid to said chambers, a hollow piston reciprocable in the large chamber and having passages through its wall, a cup on the piston for preventing ow of fluid through said passages in one direction, a concentric extension on the piston 'having a passage therein providing a communication between the large chamber and an interior chamber of the piston, a perforated collar on th'e extension, a second hollow piston movably mounted on the collar and reciprocable in the small cylinder, said second piston having an axial oriiice adapted to be closed by the extension and a plurality -of ports, a cup on the second piston for preventing flow of uid through said ports in one direction, a valve in the rstmentioned piston normally closing the interior chamber of the hollow piston from communication with the reservoir, said interior chamber being intermediate the valve and large chamber, a discharge port in the small cylinder, a spring positioned in th'e interior chamber interposed between said valve and the larger piston and acted upon by the -reactions exerted by the nuid pressures on both of said pistons, said spring being yieldable under a predetermined reaction to permit relative movement between said pistons and said valve for opening of said valve and relief of uid pressure in the larger chamber, and means forexerting force on said valve to advance said pistons.

4. A fluid pressure producing device of the class described, comprising a cylinder'having a double diametral bore providing a large chamber and a relatively small chamber, a reservoir for supplying fluid to said chambers, a piston reciprocable in the large chamber andhaving passages through its wall, a cup on the piston for preventing ow of nuid through said passages in one direction, a chamber in the piston communieating by way of a passage with thevlarge chamber, a headon the''chamber in the piston having a passage therethrough providing communication between the reservoir and the chamber in the piston, a concentric extension on the piston, a second vpiston mounted on lthe-extension and reciprocable in the small cylinder, an orifice in the small piston controlled by the extension, passages through the small piston, sealing means controlling the flow of uid through said passages in one direction, a spring-pressed valve in the piston chamber having a. part cooperating with the head on the chamber to normally close the passage through the h'ead and another part adapted to be acted upon by an actuator for advancing the piston, s aid valve during advance of the piston being acted upon by opposing forces,

said force resisting opening ot thevvalve being the-'spring load plus the fluid pressure in the the valve and relief of pressure from the larger chamber.

HERBERT C. BOWEN. 

